Worm-like

M. E. Cates, S. J. Candau. Statics and dynamics of worm-like surfactant micelles. J Phys Condens Matter 2 6869-6892, 1990. 

J. S. Pedersen, M. Laso, P. Schurtenberger. Monte Carlo study of excluded volume effects in worm-like micelles and semi-flexible polymers. Phys Rev E 54 R5917-R5920, 1996. 

If the germanium layers are partly oxidized by a short potential step to -1500 mV, random worm-like nanostructures form, healing in a complex process if the electrode potential is set back to more negative values (Figure 6.2-15). 

Semi-Flexible Chains Worm-Like Cods. 241... 

FIGURE 21.4 Nanofishing of a single polystyrene (PS) chain in cyclohexane. The solvent temperature was about 35°C (0 temperature). A cantilever with a 110 pN nm spring constant was used. The worm-like chain (WLC), solid line, and the freely jointed chain (FJC), dashed line models were used to obtain fitting curves. (From Nakajima, K., Watabe, H., and Nishi, T., Polymer, 47, 2505, 2006.)... 

As for further analysis, curve fitting against the worm-like chain (WLC) model was conducted and indicated as a solid line in Figure 21.4. The model describes single polymer chain mechanics ranging from random-coil to fully extended forms, as follows ... 

Interestingly, this behavior of the reaction mixture can be prevented by employing another principle of particle stabilization steric protection. Inclusion of pegylated comonomer (PEG-AEPD) into the reaction mixture did enable the formation of nonaggregating DNA particles. It also caused the particles to form worm -like structures (as judged by transmission electron microscopy) that have previously been observed with DNA complexes formed from block copolymers of PEL and PEG [98]. 

The worm like chain behaviour of the pectins is developped allowing to predict the dimensions of the chain as soon as the persistence length is known. The experimental data are compared with the theoretical prediction obtained from conformational analysis. 

As discussed in the last 3 years, polysaccharides behave in solution under a worm like chain [26] the local stiffness of the chain is characterized by a persistance length (Ip) the larger Ip is, the larger the chain deviates from the gaussian behaviour in the usual molecular weight range of these natural polymers [27], This makes difficult to use the relations given in litterature for synthetic... 

Figure 12.5 AFM images of thin PS-b-P4VP (20000 19000) films (3-pentanone solvent) with worm-like structures on mica substrates and height profiles of horizontal lines in these images, (a), (d) Before and (b), (e) after being doped with TCPP. (c), (f) TCPP-doped films irradiated with fluence of about ISOmJcm in air. (d)-(f) show the height profiles of the...

Figure 3 shows an electron micrograph of a representative replica region of "native" xanthan E. This native xanthan (Fig. 3) contain a large number of aggregates, whereas after exposure to 80 °C for 2 months in synthetic brine (27) this sample reveals the general features of a polydisperse, uniformly thick worm-like polymer. 

The other limiting case concerns locally smooth chains. For the case of a Gaussian chain in a network of rods, Edwards found d (L/V) 1/2 [66] which agrees with the above discussed binary contact model. Finally, considering worm-like chain bridges the differences in the power laws between the two limiting cases and exponents between — 1 and — 1/2 may be obtained. 

An electric field-induced bending of gel makes a worm-like motion feasible [18]. A weakly crosslinked PAMPS gel in a surfactant solution bends toward the anode under dc electric fields. Both ends of the gel are placed on front and rear hooks and are then hung on a plastic ratchet bar. When a varying electric field of 10 V/cm and 0.5 Hz is applied, the gel moves forward in the solution with a bending motion at a velocity of 25 cm/min. 

Meijer et al. [135] further studied aggregation phenomena of amphiphilic copolymers obtained by modifying the termini of the dendrimer units of the above series with carboxylic acid groups (49). TEM experiments indicated that all block copolymers formed large aggregates except third generation copolymer which formed worm-like micelles. 

The molar mass dependence of the intrinsic viscosity of rigid chain polymers cannot be described by a simple scaling relation in the form of Equation (36) with molar mass independent of K and a. over a broad molar mass range. Starting from the worm-like chain model, Bohdanecky proposed [29] the linearizing equation... 

Instead of the familiar sequence of morphologies, a broad multiphase window centred at relatively high concentrations (ca. 50-70% block copolymer) truncates the ordered lamellar regime. At higher epoxy concentrations wormlike micelles and eventually vesicles at the lowest compositions are observed. Worm-like micelles are found over a broad composition range (Fig. 67). This morphology is rare in block copolymer/homopolymer blends [202] but is commonly encountered in the case of surfactant solutions [203] and mixtures of block copolymers with water and other low molecular weight diluents [204,205]. 

Fig. 67 Schematic of phase behaviour for blend of novolac epoxy resin with nearly symmetric poly(methyl acrylate-co-glycidylmelhacrylate)-0-polyisoprene. Ordered L can be swollen with up to about 30% of resin before macroscopic phase separation occurs, producing heterogeneous morphologies containing various amounts of L, C, worm-like micelles and pristine epoxy. At lower concentrations, disordered worm-like micelles transform into vesicles in dilute limit. According to [201]. Copyright 2003 Wiley...

Bismuth nitrate together with sodium sulphide and tellurium oxide have been used to grow bismuth chalcogenide films.162-166 The stoichiometric ratio 2 3 has been confirmed by XPS, EDX, and XRD.162-166 The Bi2Te3 films were rough and consisted of particles with a diameter of 30-100nm, and electron probe microanalysis showed a worm-like network structure.164-166... 

TEM measurements revealed clustering of aggregates in all cases except for PS-de dr-(COOH)8 for which individual worm-like micelles were observed. 

This conjecture was found to hold for flexible chains, stiff worm-like chains, star macromolecules, and hard spheres [156]. A few results are shown in Fig. 32. 

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